It has long been known to employ screws as a type of fastener for attaching two or more components together to constitute what is essentially an integral body within the boundaries of the operating parameters of a system tending to separate the components from a base material. One particular type of connection involves the attachment of one or more components to a sheet material as by the utilization of screws. An extensive use of screw fasteners has developed in regard to attaching layers of sheet metal or attaching other components to sheet metal with what are known as tapping screws. The most basic tapping screws are threaded fasteners that have the ability to tap their own mating internal threads when driven into preformed holes in metallic and non-metallic materials. As these tapping screws were widely used in sheet-metal applications, such as ducts for heating and ventilating systems, they came to be known as “sheet-metal screws.” Another widespread usage of tapping screws is in relation to attaching components to insulated composite laminate panels having thin steel skins or a covering formed about foamed plastic materials. Extensive use of such panels is for sectional doors for commercial and residential applications, wherein a plurality of laminate panels are made into doors by attaching components, such as hinges, bottom brackets, struts, roller brackets, and other hardware necessary to the function of the door. As will be appreciated hereinafter, the present invention is particularly useful in certain applications, such as sectional door panels wherein the interior of the panel is not accessible from the outside, which require the attachment of components once the panel has been formed.
In some instances, efforts have been directed toward the use of adhesives to attach components to sheet-metal materials. However, uniform dispensing of an adhesive is extremely difficult when manually performed and is, to a substantial extent, problematical and expensive with automated equipment. If excess adhesive is applied, it creates an area on the material having excess cured adhesive in the final product, and a thicker layer takes longer to cure. If too little adhesive is applied, the ability of the adhesive to bond the component to the sheet-metal material is seriously derogated. In most instances, the adhesive must fully cure before a door panel is placed in operation, and, when cured, the adhesive must withstand the temperature extremes that a door will undergo in its normal service environment. Depending upon the type of production line and the rate of production, problems are encountered if the components to be attached are allowed to set for several minutes before being installed. In instances of such a delay, the adhesive may harden to such an extent that the glued components must be discarded. At the other end of the spectrum, most adhesives for applications of this type take several hours to fully cure. In many instances, the panels are packaged at the conclusion of the production line before the adhesive is cured, such that movement of the components on the sheet-metal material may occur during packaging, resulting in misalignment of the components, which produces later installation or operational problems in the inability of the components to precisely interact with other elements. Finally, installers and consumers are unable to successfully replace a damaged or missing component by the use of adhesives in the field, such that panels must be replaced in their entirety when replacement of a component is necessary.
For many years in the sectional door and other fields, the use of tapping screws has been a highly popular means of securing components to the sheet metal. During most of the time period, sheet metals for sectional doors and many applications have been of a thickness greater than 0.032 of an inch, which has provided sufficient material thickness to allow the screw to tighten and apply compressive forces to the component without stripping the screw threads formed in the sheet-metal material by the screw. In this normal practice, the component to be fastened to the sheet-metal material has a clearance hole somewhat larger than the screw and the sheet-metal is drilled or perforated by the screw and the component is secured to the sheet-metal material by tightening the screw and applying a compressive force against the component.
In recent years, strides have been made in the sectional door and related industries to create panels with reduced quantities of raw materials while retaining comparable strength and temperature-resistant characteristics. In this respect, many manufacturers are employing sheet-metal materials having a thickness which is substantially less than 0.032 of an inch while providing foam adhesion and reinforcing characteristics that maintain comparable strength in the overall panel configuration. The use of sheet-metal screws to attach components to sheet metal having a thickness substantially less than 0.032 of an inch typically results in the screws stripping the screw threads formed in the sheet-metal material before adequate compressive forces can be applied against the component, or the sheet metal will at least deteriorate in the area of the screw hole, causing a drop in the compressive force against the component, which may produce loosening or failure due to fatigue factors once the panel is placed in service.
Due to the desirability and feasibility of employing thinner sheet-metal materials, various developments have been made to permit the attachment of components to sheet metal having a thickness substantially less than 0.032 of an inch. One widely-adopted approach is to employ reinforcing members made of thicker, normally metallic materials on the other side of the sheet metal from the component to be attached to sandwich the thin sheet metal between the component and the reinforcing member. In the instance of sheet-metal panels or other closed bodies or where foam or other insulation is provided within the panel, the installation of the reinforcing members must occur prior to completing formation of the panel configuration and/or the foaming process. In such instances, the reinforcing members must be held precisely positioned until such time as the external component is installed on a panel. In most instances, the reinforcing members are temporarily secured by an adhesive, which creates a number of processing steps that often create additional problems. In order to achieve desirable production rates, highly-expensive automated equipment is required for ease of application of the glue and automated positioning of the reinforcing members. Whether automated equipment is employed or the application of adhesive and reinforcing members is effected manually, it is inevitable that on occasion the reinforcing members will not be precisely positioned, may come loose during subsequent processing, or are no longer precisely positioned, such that the screws do not properly secure the components to the panel, which, as a result, must be discarded. Further, in the case of such panel members, it is not always known if the reinforcing member is properly positioned and adhered until the door is installed in the field. The replacement or repair of a panel in the field is extremely time consuming and costly, particularly if the panel must be replaced due to a defectively-placed or adhered reinforcing member.
Another approach for attaching components to a thin sheet-metal panel having a thickness substantially less than 0.032 of an inch is by through-bolting of the component to the panel. In such instance, a longer screw or bolt, which extends entirely through the panel and is secured by a nut or a reinforcing member on the opposite side of the panel, is employed. This, in effect, sandwiches both skins of the sheet-metal material. In most instances, this approach is viewed as highly undesirable due to the appearance of the nut or bolt head on both sides of the panel and because a thin sheet-metal panel of this type may compress over a period of time, thereby lessening the retaining ability of the bolt. In addition, the external threading of the nut requires additional time, and, depending on the circumstances, a second person may be required to accomplish the installation.
Another technique for developing adequate material thickness to retain sheet-metal screws without stripping in thin sheet metals involves what is termed a “hemming” process. In this approach, the edge of the skins are folded over or hemmed to create two or more thicknesses of the sheet-metal material, thereby producing a sufficient cumulative material thickness to retain sheet-metal screws. Since the use of a uniform material width requires that the hem extend the entire length of a panel, the material cost of this approach is extremely high, and unnecessary weight is added to the door when only very limited extents of a longitudinal hem is actually used to attach the components.
Finally, in other instances, fasteners other than sheet-metal screws have been applied to thin sheet-metal materials to attach components thereto in the form of various types of rivets. In this respect, applications have considered tubular, semi-tubular, and solid rivets; however, as is the case with screws, rivets apply fastening tension over a relatively small area adjacent to the sheet-metal material hole and have not been successfully employed in fastening components to thin sheet-metal skins without adding a reinforcing member to the inside of the skin to sandwich the sheet-metal skin in the manner above described. Thus, while many approaches have been employed for attaching components to thin sheet-metal materials, essentially all that provide an operative solution involve additional materials, additional cost, and/or additional processing steps, which tend to reduce production rates.